Integrated detonators for use with explosive devices

ABSTRACT

A detonator assembly is provided for use in oilfield operations to detonate an explosive downhole including a capacitor discharge unit and initiator electrically connected together to form a single unit. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

CROSS-REFERENCE TO RELATED APPLICATIONS

This claims the benefit under 35 U.S.C. § 119(e) of U.S. ProvisionalPatent Application Ser. No. 60/521,088, entitled,“MICROELECTROMECHANICAL DEVICES,” filed on Feb. 19, 2004. This is also acontinuation-in-part of U.S. Ser. No. 10/304,205, filed Nov. 26, 2002,which claims the benefit under 35 U.S.C. § 119(e) of U.S. ProvisionalPatent Application Ser. No. 60/333,586, entitled, “INTEGRAL CAPACITORDISCHARGE UNIT,” filed on Nov. 27, 2001.

BACKGROUND

The present invention relates generally to activating devices, and moreparticularly to an integrated detonator for use in activatingexplosives.

Explosives are used in many types of applications, such as hydrocarbonwell applications, seismic applications, military armament, and miningapplications. In seismic applications, explosives are discharged at theearth surface to create shock waves into the earth subsurface so thatdata regarding the characteristics of the subsurface may be measured byvarious sensors. In the hydrocarbon well context, a common type ofexplosive that is used includes shaped charges in perforating guns. Theshaped charges, when detonated, create perforating jets to extendperforations through any surrounding casing or liner and into thesurrounding formation to allow communication of fluids between theformation and the wellbore. Also, in a well, other tools may alsocontain explosives. For example, explosives can be used to set packersor to activate other tools.

To detonate explosives, detonators are used. Generally, detonators canbe of two types: electrical and percussion. A percussion detonatorresponds to some type of mechanical force to activate an explosive. Anelectrical detonator responds to a predefined electrical signal toactivate an explosive. One type of electrical detonator is referred toas an electro-explosive device (EED), which may include hot-wiredetonators, semiconductor bridge (SCB) detonators, exploding bridge wire(EBW) detonators, or exploding foil initiator (EFI) detonators.

With certain types of electrical detonators, a local electrical sourceis placed in the proximity of the detonator. Such an electrical sourcemay be in the form of a capacitor discharge unit that includes acapacitor that is charged to a predetermined voltage. In response to anactivation signal, the charge stored in the capacitor is discharged intoanother device to perform a detonation operation. Typically, due to therelatively large amount of energy that is needed, the capacitordischarge unit can be quite large, which leads to increased sizes ofhousings in downhole tools that contain such capacitor discharge units.Further, because of relatively large sizes, the efficiencies ofconventional capacitor discharge units are reduced due to increasedresistance and inductance of electrical paths in a detonator.

SUMMARY

In general, an improved detonator is provided that is smaller in sizeand that is more efficient. For example, in one embodiment, a detonatorassembly includes an energy source (e.g., a capacitor) having a surface,the energy source further having electrodes. A resistor is formed on thesurface of the energy source, with one end of the resistor beingelectrically connected to one of the electrodes.

In some example embodiments, resistors are formed on the surface of thecapacitor with thick-film deposition. For example, one type of resistoris a charging resistor. Another type of resistor is a bleed resistorthat connects the two electrodes. The surface of the capacitor is usedto attach electrically a switch and/or an initiator, such as anexploding foil initiator (EFI).

In other example embodiments, an improved detonator includes an EFI,switch, capacitor, bleed resistor, transformer, and addressable chipintegrated to form a monolithic unit having the size of a conventionalhot-wire detonator. The monolithic unit may also include a lineprotection filter and an explosive.

In another example embodiment, an improved detonator may be embedded ina tubing cutter or used to initiate the firing of a tubing cutter or jetcutter. Alternatively, an embodiment of the improved detonator may beused to initiate one or more shaped charges.

Other features and embodiments will become apparent from the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate two tool strings according to someembodiments of the invention.

FIG. 2 is a schematic electrical diagram of a detonator assembly thatcan be used in the tool string according to FIG. 1A or 1B.

FIG. 3 is a perspective view of the detonator assembly.

FIG. 4 is a bottom view of the detonator assembly.

FIG. 5 is a schematic side view of a capacitor in the detonatorassembly.

FIGS. 6 and 7 illustrate two different types of switches used in thedetonator assembly of FIG. 2.

FIGS. 8A and 8B illustrates an embodiment of the micro-switch of thepresent invention as used in an integrated detonator device.

FIG. 9 illustrates an example of the addressable functionality of anembodiment of the integrated detonator device of FIGS. 8A and 8B.

FIG. 10 illustrates an example of an embodiment of the voltage step-uptransformer of the integrated detonator device.

FIG. 11 illustrates an embodiment of the triggered spark gap circuitryof the integrated detonator device.

FIG. 12 illustrates an embodiment of the piezoelectric transformer ofthe integrated detonator device.

FIG. 13A-B illustrate an embodiment of the jet cutter of the integrateddetonator device.

FIGS. 14A-C illustrate an embodiment of the present invention for use indetonating a shaped charge or a set of shaped charges in a shot-by-shotoperation to achieve selective firing.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details and that numerous variations ormodifications from the described embodiments may be possible.

As used herein, the terms “connect”, “connection”, “connected”, “inconnection with”, and “connecting” are used to mean “in directconnection with” or “in connection with via another element”; the terms“mechanically connect”, “mechanical connection”, and “mechanicallyconnected”, “in mechanical connection with”, and “mechanicallyconnectiong” means in direct physical connection to form a monolithicunit such as bonded, fused, or integrated; and the term “set” is used tomean “one element” or “more than one element”; the terms “up” and“down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and“downstream”; “above” and “below”; and other like terms indicatingrelative positions above or below a given point or element are used inthis description to more clearly describe some embodiments of theinvention. However, when applied to equipment and methods for use inwells that are deviated or horizontal, such terms may refer to a left toright, right to left, or other relationship as appropriate. As usedhere, the terms “up” and “down”; “upper” and “lower”; “upwardly” anddownwardly”; “above” and “below”; and other like terms indicatingrelative positions above or below a given point or element are used inthis description to more clearly describe some embodiments of theinvention. However, when applied to equipment and methods for use inwells that are deviated or horizontal, or when such equipment are at adeviated or horizontal orientation, such terms may refer to a left toright, right to left, or other relationship as appropriate.

Referring to FIG. 1A, an embodiment of a tool string includes aperforating string having a perforating gun 20 and a firing head 18. Theperforating string is attached at the end of a carrier line 12, such asa wireline, electrical cable, slickline, tubing, and so forth. In theembodiment of FIG. 1A, the firing head 18 includes an exploding foilinitiator (EFI) detonator assembly 22 according to one embodiment. Asdiscussed below, the EFI detonator assembly 22 includes an integratedassembly of a capacitor discharge unit (CDU) and EFI. It should benoted, in the embodiments using wireline or tubing to suspend theperforating string, a downhole battery may be used to supply power tothe EFI.

More generally, the integrated capacitor discharge unit has a capacitorand a charging and bleed resistor. The integrated capacitor dischargeunit includes a thick-film circuit that electrically connects thecapacitor and the resistor, as well as other components.

The detonator assembly 22 is coupled to a detonating cord 24, which isconnected to a number of shaped charges 26. Activation of the detonatorassembly 22 causes initiation of the detonating cord 24, which in turncauses detonation of the shaped charges 26. Detonation of the shapedcharges 26 causes the formation of perforating jets from the shapedcharges 26 to extend openings into the surrounding casing 10 and toextend perforation tunnels into the surrounding formation 14.

FIG. 1B shows another embodiment of the perforating string, whichincludes a firing head 30 and a perforating gun 32. The perforating gun32 also includes multiple shaped charges 34. However, instead of theshaped charges 34 being connected to a detonating cord, each shapedcharge 34 is associated with a respective local detonator assembly 36.In one embodiment, each of the detonator assemblies 36 includes EFIdetonator assemblies that are configured similarly to the detonatorassembly 22 of FIG. 1A. The detonator assemblies 36 are connected by anelectrical cable 38, which provides an electrical signal to thedetonator assemblies 36 to activate such detonator assemblies. Thefiring head 30 receives a remote command from elsewhere in the wellbore16 or from the surface of the wellbore.

A benefit offered by the perforating string of FIG. 1B is that theshaped charges 34 can be substantially simultaneously detonated inresponse to an activating signal or voltage supplied down the electricalcable 38, or fired in any desired sequence or with any desired delay.This is contrasted to the arrangement of FIG. 1A, where detonation ofsuccessive shaped charges 26 is delayed by the speed of a detonationwave traveling down the detonating cord 24.

Although the arrangement of FIG. 1B includes multiple detonatingassemblies 36, as compared to the single detonator assembly 22 in thearrangement of FIG. 1A, the small size of the detonating assemblies 36according to some embodiments allows such detonating assemblies to beincluded in the perforating gun 32 without substantially increasing thesize of the perforating gun 32.

As noted above, in one embodiment, an electrical signal is provided tothe firing head 22 or 30 to activate the perforating gun 20 or 32.However, in alternative embodiments, the activating signal can be in theform of pressure pulse signals, hydraulic pressure, motion signalstransmitted down the carrier line 12, and so forth.

Instead of perforating strings, detonator assemblies according to someembodiments can be used in other types of tool strings. Examples ofother tool strings that contain explosives include the following: pipecutters, setting devices, and so forth. Also, detonator assembliesaccording to some embodiments can also be used for other applications,such as seismic applications, mining applications, demolition, ormilitary armament applications. In seismic applications, the detonatorassemblies are ballistically connected to explosives used to generatesound waves into the earth sub-surface for determining variouscharacteristics of the earths sub-surface.

As noted above, in one embodiment, the detonator assembly 22 includes anEFI detonator assembly. EFIs include an exploding foil “flyer plate”initiator or an exploding foil “bubble activated” initiator. Other typesof detonator assemblies can use other types of electrical initiators,such as exploding bridge wire (EBW) initiators and semiconductor bridge(SCB) initiators.

As shown in FIG. 2, an electrical schematic diagram of one embodiment ofa detonator assembly 100. The detonator assembly 100 can be either thedetonator assembly 22 of FIG. 1A or the detonator assembly 36 of FIG.1B. The detonator assembly 100 includes a capacitor discharge unit (CDU)102, an EFI 104, and a high explosive (HE) 106.

The CDU 102 includes a capacitor 108, a charging resistor 110, and ableed resistor 112. In addition, the CDU 102 includes a switch 114 forcoupling charge stored in the capacitor 108 to the EFI 104 to activatethe EFI 104. When activated, the EFI 104 produces a flyer that ispropelled at usually hyper-sonic velocity and traverses a gap 116 toimpact the high explosive 106. In some embodiments, the flyer may befabricated from a metal-foil or polymer-foil material. The impact of theflyer against the high explosive 106 causes detonation of the explosive106. The explosive 106 is ballistically coupled to either the detonatingcord 24 (FIG. 1A) or to an explosive of a shaped charge 34 (FIG. 1B). Insome embodiments, the internal resistance of the capacitor may besufficient and a separate charging resistance not necessary.

The capacitor 108 is charged by applying a suitably high DC voltage atline 118. The voltage is supplied through the charging resistor 110 intothe capacitor 108. The charging resistor 110 is provided for limitingcurrent (in case of a short in the capacitor 108 or elsewhere in the CDU102). The charging resistor 110 also provides isolation of the CDU 102from other CDUs in the tool string.

The bleed resistor 112 allows the charge in the capacitor 108 to bleedaway slowly. This is in case the detonator assembly 100 is not firedafter the tool string has been lowered into the wellbore. The bleedresistor 112 prevents the CDU 102 from becoming a safety hazard when atool string with un-fired detonator assemblies 100 have to be retrievedback to well surface.

In other embodiments, other detonator assemblies with other types ofenergy sources (other than the capacitor 108) can be employed.

The detonator assembly 100 includes an integrated assembly of the CDU102 and EFI 104 to provide a smaller detonator assembly package as wellas to improve efficiency in performance of the detonator assembly 100.Efficient CDUs need to have fast discharge times (such as nanosecondreaction rates through a low inductance path) through the EFI with lowenergy loss (low resistance). One way to increase the efficiency is toreduce as much as possible the inductance (L) and resistance (R) of thetotal circuit in the discharge loop of the CDU 102. By integrating theCDU 102 into a smaller package, the inductance and resistance can bereduced, thereby improving the efficiency of the CDU 102.

According to some embodiment of the invention, the charging resistor 110and bleed resistor 112 are implemented as resistors formed on a surfaceof the capacitor 108. Further, in some embodiments, the switch 114 isalso integrated onto the surface of the capacitor 108, which furtherreduces the overall size of the CDU 102.

FIG. 3 shows the CDU 102 according to one embodiment. The capacitor 108in one embodiment includes a ceramic capacitor, which has an outerceramic housing 202 formed of a ceramic material. However, in otherembodiments, other types of capacitors can be used. The capacitor 108includes a first group of one or more electrically conductive layersthat are connected to one electrode, referred to as a cathode. A secondgroup of one or more electrically conductive layers in the capacitor 108are connected to another electrode of the capacitor, referred to as ananode. One or more layers of dielectric material are provided betweenthe cathode and anode electrically conductive layers. The cathodelayers, anode layers, and dielectric layers are provided inside theouter housing 202 of the capacitor 108. As shown in FIG. 3, thecapacitor 108 has a first electrode 204 and second electrode 206. Theelectrodes 204 and 206 form the cathode and anode of the capacitor 108.

The capacitor electrode 206 is electrically contacted to an electricalwire 208. Another electrical wire 210 is connected to a node of thecharging resistor (not shown in FIG. 3), which is formed on the lowersurface 212 of the capacitor 108.

Further, the EFI 104 is attached on an upper surface 222 of thecapacitor 108. One side of the EFI 104 is connected by an electricallyconductive plate 215 to the electrode 206 of the capacitor 108. Theother side of the EFI 104 is electrically connected to an electricallyconductive plate 214, which is in turn connected to one side of theswitch 114. The other side of the switch 114 is electrically connectedby another electrically conductive plate 216 to the capacitor electrode204. Electrical connections are provided by thick-film deposition, orother equivalent methods. Any number of types of small switches can beused, such as those disclosed in U.S. Pat. No. 6,385,031 and U.S. Ser.No. 09/946,249, filed Sep. 5, 2001, both hereby incorporated byreference. Also, the EFI may include an integral switch as part of itsconstruction.

A bottom view of the CDU 102 is shown in FIG. 4. The bleed resistor 112and charging resistor 110 are both arranged as thick-film or thin-filmresistors on the lower surface 212 of the capacitor 108. One end 302 ofthe bleed resistor 112 is electrically connected to the electrode 204,while the other end 304 of the resistor 112 is electrically connected tothe electrode 206. One end 306 of the charging resistor 110 iselectrically connected to the electrode 204, while the other end 308 ofthe resistor 110 is electrically connected to a contact pad 310. Thecontact pad 310 allows electrical connection of charging the resistor110 with the electrical wire 210.

The material and geometry (thickness, length, width) of each resistor110 and 112 are selected to achieve a target sheet resistance so thatdesired resistance values of resistors 110 and 112 can be achieved. Inother embodiments, instead of thick-film or thin-film resistors, othertypes of resistors that can be deposited, bonded, or otherwise formed onthe capacitor housing can be used.

To form the resistors on a surface (or surfaces) of the capacitorhousing, a groove or notch can be formed in the outer surface(s) of thecapacitor housing, followed by the deposition or introduction ofresistance material into the groove or notch. Alternatively, a resistivematerial may be silk-screened or printed onto the surface(s), or othertechniques may be used.

FIG. 5 shows a schematic representation of the layers of the capacitor108. Electrically conductive layers 312 are connected to the firstelectrode 204, while electrically conductive layers 314 are connected tothe electrode 206. In some embodiments, the electrically conductivelayers 312 and 314 are formed of a metal, such as copper,silver-palladium alloy, or other electrically conductive metal.Dielectric layers are provided between successive layers 312 and 314.

According to one embodiment, the switch 114 (FIG. 2) is implemented asan over-voltage switch. As shown in FIG. 6, one embodiment of theover-voltage switch 114 includes a first electrically conductive layer402 and a second electrically conductive layer 406. Interposed betweenthe electrically conductive layers 402 and 406 is an insulating(dielectric) layer 404. In one example implementation, the electricallyconductive layers 402 and 406 are formed of copper or other electricallyconductive metal. In one example implementation, the insulating layer404 is formed of a polyimide material.

The insulating layer 404 has a thickness and a doping concentrationcontrolled to cause the switch 114 to activate at a selected voltagedifference between electrically conductive layers 402 and 406. Once thevoltage crosses over some predefined threshold level, the insulatinglayer 404 breaks down to electrically connect the first and secondelectrically conductive layers 402 and 406 (thereby closing the switch114).

Optionally, the breakdown voltage of the insulating layer 404 can becontrolled by having the geometry of overlapping electrically conductivelayers 402 and 406 be somewhat pointed to increase the potentialgradient at the points. Further, depositing a hard metal such astungsten on contact areas of the first and second electricallyconductive layers 402 and 406 can prevent burn-back of the electricallyconductive layers. The contact areas are provided to electricallyconnect the electrically conductive layers 402 and 406 to respectivewires. The hardened metal also provides for a more efficient switch.Also, for increased efficiency, the gap distance between points is madesmall, such as on the order of a few thousands of an inch.

FIG. 7 illustrates another type of switch 114. This alternative switchis a triggered switch that adds another electrically conductive layerthat is connected to a trigger voltage. As shown in FIG. 7, thetriggered switch 114 includes top and bottom electrically conductivelayers 410 and 414, in addition to an intermediate electricallyconductive layer 412. Insulating layers 416 and 418 are provided betweensuccessively electrically conductive layers. In operation, a highvoltage (reference to ground) with a fast rise time is applied to thetrigger anode 412. The trigger voltage has sufficient amplitude to causethe insulating layers 416 and 418 to break down to allow conductionbetween the top and bottom electrically conductive layers 410 and 414.

In other embodiments of the detonator of the present invention,micro-switches may be integrated to form a small, low-cost detonatorutilizing Exploding Foil Initiator technology. For example, in oneembodiment, a micro-switchable EFI detonator is small enough to fitinside a standard detonator housing, thereby simplifying logistics andpackaging, easing assembly, and improving overall reliability whilereplacing the less safe hot-wire detonator. A “micro-switch” may be usedas disclosed in U.S. Ser. No. 10/708,182, filed Feb. 13, 2004, which ishereby incorporated by reference. Such a micro-switch may include, butis not limited to, a microelectromechanical system (MEMS) switch, aswitch made with microelectronic techniques similar to those used tofabricate integrated circuit devices, a bistable microelectromechanicalswitch, a spark gap switch, a switch having nanotube electron emitters(e.g., carbon nanotubes), a metal oxide silicon field-effect transistor(MOSFET), an insulated gate field-effect transistor (IGFET), and othermicro-switching devices.

With respect to FIGS. 8A and 8B, in general, an embodiment of thepresent invention may include a small, monolithic detonator 800 with allcomponents integrated into a single unit. The components may include,but are not limited to: an integrated capacitor discharge unit 808including a charging resistor and bleeder resistor that are fused orbonded together with a micro-switch and an initiator (e.g., an EFI, EBW,SCB, hot-wire, or other initiator), an initiating explosive 806, aconventional explosive 804 (e.g., PETN, RDX, HMX, CL-20, HNS, NONAand/or other explosive), a step-up transformer 810 for receiving a lowvoltage input and stepping up to a high voltage output, and anaddressable chip 812. In another embodiment, a microchip may be employedfor ease of design. The resultant size of the integrated detonator 800is small enough to be packaged inside a standard detonator housing 802and may receive power via a standard plug 814.

An embodiment of the detonator 800 has a size and shape substantiallyequal to that of a standard cylindrical hot-wire detonator. For example,some standard hot-wire detonators have a cross-sectional diameter ofapproximately 0.28 inches. In another example, an embodiment of thedetonator 800 may have the same diameter as the detonating cord 24 (FIG.1A) to which the detonator is coupled. This relatively small-sizeddetonator may be desirable over large-sized prior art detonators, whichgenerally consist of a bulky capacitor discharge unit (CDU) (includingan EFI, gas-tube switch, bleeder resistor, and capacitor), together witha multiplier, smart electronics, and explosive packaged in a relativelylarge housing having a 0.75 inch diameter cross section. The relativelylarge size of these prior art detonators limits their application andfield use, as well as increases the cost of manufacturing. While thisembodiment of the detonator of the present invention has across-sectional diameter of approximately 0.28 inches, it is intendedthat other embodiments may include integrated detonators having othercross-sectional diameters.

Besides having a smaller overall size, embodiments of the detonator 800of the present invention may include various advantages over prior artdetonators for facilitating safe arming and firing. Some embodimentshave an added advantage of firing at lower voltage. For example, thedetonator may be configured to respond to a firing voltage of as low asapproximately 30 volts. Moreover, some embodiments of the detonator 800include a radio frequency identification (RFID) tag to facilitate securearming and triggering functions, as well as providing for identificationand inventory control. Additionally, embodiments of the detonator may berated for operation in temperatures up to approximately 340° F. Highertemperatures (up to approximately 500° F.) may be achieved with theinclusion of a thermal-delay vessel. Still other embodiments of thedetonator may be fluid desensitized, radio frequency safe, and/orprotected from unintended surface power.

With respect to FIGS. 8A and 8B, an embodiment of the detonator assembly800 may include a capacitor 808 (cylindrical or rectangular) formed froma dielectric/polarized material having a built-in (e.g., thick film)bleed resistor on one end and having a EFI and micro-switch mounted onthe other end. The EFI may be fused or bonded to the capacitor 808 and amicro-switch for activating the EFI may be located on the same substrateas the EFI or, alternatively, on a separate substrate. The micro-switchmay be an over-voltage type in a miniaturized chamber, and, in someembodiments, the micro-switch may be enhanced by carbon nanotubes asdescribed in U.S. Ser. No. 10/708,182.

Still with respect to FIGS. 8A and 8B, an embodiment of the detonatorassembly 800 may also include a step-up transformer 810 as illustratedin the circuit diagram of FIG. 10. The transformer may be fabricatedsuch that it is fused or bonded directly to the capacitor 800. Thetransformer may be capable of receiving a low-voltage input (e.g., 5 to30 volts) and stepping up to a high voltage output (e.g., 1400 volts)via a separate high-voltage diode. In some embodiments, the transformermay be fabricated from a metallic, ceramic, or ceramic-ferrite materialhaving high magnetic permeability characteristics using a conventionalwire wind process or low temperature co-fired ceramic (LTCC) processusing silk-screened conductor coils.

Further with respect to FIGS. 8A, 8B, and 10, an embodiment of thedetonator assembly 800 may also include an addressable chip 812. Theaddressable chip 812 may facilitate control selectivity and provideadded safety against accidental firing. The inclusion of an addressablechip 812 is made possible due to the low-voltage input of thetransformer 810, which facilitates packaging addressability into thechip 812. The addressable chip 812 may be designed for standard CMOSintegration with 5-volt or 3.3-volt operation using logic state machine.Moreover, some embodiments of the chip may be configured to havebuilt-in digital signal processing for improved down-link signalrecognition and an up-link using a bi-phased current loop.

In operation, an embodiment of the chip 812 facilitates the integrationof electronic addressable functions such as: (1) uniquely identifies andselects one or more explosive initiators from a set of initiators; (2)enables the selective charging and firing of the one or more initiatorsand allows programming of a specific time delay; (3) enables sleep mode,or inactive state, timing delay mode, arm and fire modes and switchingmodes to open or close reselected circuit; (4) enables sensor mode tomonitor signal from sensors (e.g., pressure, temperature, tilt angle,current, voltage, etc.); and/or (5) enables disconnect mode todisconnect bottom-fired initiators from the rest of the string bysensing a sufficient rise in current, with following progression. Anillustration of the above-identified functionality is shown in FIGS. 9and 10. It is intended that the addressable chip may be configured toperform one or all of these functions and others.

For example, an embodiment of the detonator having an addressable chipmay provide a method to trigger the detonator based on an internal timeror external trigger mechanism. Furthermore, the addressable chip mayinclude common commands to start multiple timers in a detonation string.Each timer could be preset to provide precise delays among the string.This precise control of time delays among the string enables theproduction of beneficial dynamic pressure-time characteristics. Forexample, U.S. Pat. No. 6,598,682—regarding dynamic pressure underbalanceand overbalance control—discloses a system to optimize the performanceof the perforation process as well as to limit the collateral damage ofthe gun system and other wellbore equipment by limiting the peakover-pressure and destructive pressure wave resonances and pressure wavereinforcements.

With respect to FIG. 11, another embodiment of the present inventionprovides a method to generate a trigger pulse by stepping up the slappercapacitor voltage using a second transformer of a type including, butnot limited to, low temperature co-fired ceramic, LTCC, tape wound, aircore, and/or super-cooled amorphous core. This trigger pulse enablescontrolled and accurate timing of the detonator's firing and moreefficient charging of the slapper capacitor because it can be fullycharged before it is triggered to fire the detonator. Whereas the sparkgap fires whenever its threshold voltage is exceeded, the triggercircuit and trigger electrode provides alternatives for the controlledfiring of the spark gap—for example, upon command from the surface, uponcompletion of a pre-programmed time delay, or, if a pressure sensormeasurement is also employed, upon attainment of a pre-set threshold ofpressure or pressure profile with time.

Another embodiment of the present invention provides a method togenerate a trigger pulse by supplying voltage generated using apiezoelectric mechanical transformation, as shown schematically in FIG.12. Compared to conventional transformers, this is an alternativetriggering method achieves the benefits described above for moreaccurate and efficient detonator firing. This piezoelectric method alsooffers advantages of lower components parts count, smaller package size,and lower voltage drive by the integrated circuit.

The small size of the present invention enables the novel andadvantageous ability to initiate the firing of a jet cutter from itsgeometric center. As illustrated in FIGS. 13A and 13B, the jet cutterincludes an explosive material formed intimately against a metallicliner. The liner is configured substantially about a central axissubstantially to the shape of a conical frustum between a normallytruncated apex and a normally truncated base. The EFI (or otherinitiator) with its associated CDU is positioned such that its explosivepellet is located at the center of the cutter. The EFI/CDU is attachedby a pair of simple wires through the explosive center. Alternately, asshown in FIG. 13B, the EFI may be attached by a low inductance, highvoltage cable to an external CDU, which is initiated by an electricalsignal. In any case, the benefits of the present invention includeachievement of a centered jet cutter initiation, which translates tooptimum cutter performance, no external electronics or detonating cord,only simple wires from the center of the cutter, and the improved safetyof this RF safe and addressable detonator.

Moreover, with respect to FIGS. 14A-C, instead of being embedded in ajet cutter, embodiments of the EFI/CDU unit may be substantiallyembedded in or connected directly to a shaped charge having an explosivematerial having a truncated base and formed intimately against a liner.As with the jet cutter, the EFI/CDU may be attached by a pair of simplewires (FIG. 14B), or, alternatively, the EFI may be attached by a lowinductance, high voltage cable to an external CDU, which is initiated byan electrical signal (FIG. 14C). Either of these arrangements may beused in detonating a series of shaped charges in a shot-by-shotoperation to achieve selective firing (FIG. 14A).

While the invention has been disclosed with respect to a limited numberof embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover such modifications and variations as fall within the truespirit and scope of the invention.

1. A detonator assembly, comprising: a capacitor; an initiatormechanically and electrically connected to the capacitor; a transformermechanically and electrically connected to the capacitor; and anaddressable chip mechanically and electrically connected to thetransformer, wherein the capacitor, initiator, transformer, andaddressable chip form an integrated detonating unit.
 2. The detonatorassembly of claim 1, further comprising a capacitor discharge unit, thecapacitor discharge unit comprising the capacitor and a resistor.
 3. Thedetonator assembly of claim 2, wherein the capacitor discharge unitfurther comprises a thick-film circuit that electrically connects thecapacitor and the resistor.
 4. The detonator assembly of claim 3,wherein the resistor comprises a bleeder resistor formed by thick-filmdeposition, the bleeder resistor adapted to bleed charge form thecapacitor.
 5. The detonator assembly of claim 4, wherein the resistorcomprises a charging resistor formed by thick-film deposition, thecharging resistor adapted to receive a charging voltage for thecapacitor.
 6. The detonator assembly of claim 2, wherein the capacitordischarge unit further comprises an integrated micro-switch, themicro-switch adapted electrically to couple the charge from thecapacitor to the initiator when activated.
 7. The detonator assembly ofclaim 6, wherein the micro-switch comprises one of amicroelectromechanical system switch, a bistable microelectromechanicalswitch, a spark gap switch, a switch having nanotube electron emitters,a MOSFET, and an IGFET.
 8. The detonator assembly of claim 1, whereinthe initiator comprises one of a semiconductor bridge, exploding bridgewire, and exploding foil initiator.
 9. The detonator assembly of claim2, wherein the initiator comprises an exploding foil initiator fuseddirectly to the capacitor discharge unit.
 10. The detonator assembly ofclaim 1, further comprising an explosive proximate the initiator. 11.The detonator assembly of claim 2, wherein the capacitor is fabricatedfrom a dielectric ceramic material.
 12. The detonator assembly of claim2, wherein the resistor is selected from the group consisting of athick-film resistor and a thin-film resistor.
 13. The detonator assemblyof claim 1, wherein the transformer is a piezoelectric transformer. 14.The detonator assembly of claim 1, further comprising a secondtransformer adapted to generate a trigger pulse to fire the initiator.15. The detonator assembly of claim 1, wherein the addressable chip isadapted to identify one or more initiators from a set of initiators. 16.The detonator assembly of claim 15, wherein the addressable chip isadapted to selectively charge one or more initiators from the set ofinitiators.
 17. The detonator assembly of claim 15, wherein theaddressable chip is adapted to selectively delay for a predeterminedtime the charging of one or more initiators from the set of initiators.18. The detonator assembly of claim 15, wherein the addressable chip isadapted to selectively fire one or more initiators from the set ofinitiators.
 19. The detonator assembly of claim 15, wherein theaddressable chip is adapted to selectively delay for a predeterminedtime the firing of one or more initiators from the set of initiators.20. The detonator assembly of claim 1, wherein the addressable chip isadapted to inactivate the initiator.
 21. The detonator assembly of claim1, wherein the addressable chip is adapted to activate a sensor.
 22. Thedetonator assembly of claim 21, wherein the sensor is a pressure sensor.23. The detonator assembly of claim 21, wherein the sensor is atemperature sensor.
 24. The detonator assembly of claim 21, wherein thesensor is a tilt-angle sensor.
 25. The detonator assembly of claim 21,wherein the sensor is a current sensor.
 26. The detonator assembly ofclaim 21, wherein the sensor is a voltage sensor.
 27. The detonatorassembly of claim 21, wherein the sensor is a radio frequency sensoradapted to detect radio frequency identification tags.
 28. The detonatorassembly of claim 1, wherein the addressable chip is adapted todisconnect a bottom-fired initiator from a string of initiators.
 29. Thedetonator assembly of claim 1, further comprising a housing adapted tohold the detonating unit.
 30. The detonator assembly of claim 29,wherein the housing has an outer diameter of approximately 0.28 inches.31. The detonator assembly of claim 29, wherein the housing is adaptedto couple with a detonating cord having a predetermined diameter. 32.The detonator assembly of claim 31, wherein the housing has an outerdiameter substantially equal to the diameter of the detonating cord. 33.A method of fabricating an integrated detonator, comprising: providing acapacitor discharge unit; mechanically and electrically connecting atransformer to the capacitor discharge unit; mechanically andelectrically connecting an addressable chip to the transformer; andelectrically connecting a micro-switch and initiator to the capacitordischarge unit.
 34. The method of claim 33, wherein providing acapacitor discharge unit comprises mechanically and electricallyconnecting a resistor and a capacitor.
 35. The method of claim 33,further comprising providing an explosive proximate the initiator.
 36. Ajet cutter, comprising: a first explosive material formed intimatelyagainst a metallic liner; and a detonator assembly substantiallyembedded in the first explosive material, the detonator assemblycomprising an initiator, a capacitor, and a second explosive materialproximate the initiator.
 37. The jet cutter of claim 36, wherein theinitiator and capacitor are fused or bonded together to form a singleunit.
 38. The jet cutter of claim 36, wherein the capacitor is locatedexternal to the first explosive material, and wherein the initiator andcapacitor are electrically connected together by a cable.
 39. A shapedcharge, comprising: a first explosive material formed intimately againsta metallic liner; and a detonator assembly comprising an initiator, acapacitor, and a second explosive material proximate the initiator,wherein the second explosive material is in direct contact with thefirst explosive material.
 40. The shaped charge of claim 39, wherein theinitiator and capacitor are mechanically connected to form an integratedunit.
 41. The shaped charge of claim 39, wherein the capacitor islocated external to the first explosive material, and wherein theinitiator and capacitor are electrically connected together by a cable.42. A detonator assembly, comprising: a capacitor discharge unit, thecapacitor discharge unit comprising a charging resistor, a bleederresistor, and a capacitor mechanically and electrically connectedtogether; an initiator mechanically and electrically connected to thecapacitor discharge unit, the initiator selected from the groupconsisting of an exploding foil initiator, an exploding bridge wire, asemiconductor bridge, and a hot wire; a micro-switch mechanically andelectrically connected to the capacitor discharge unit and theinitiator; an initiating explosive proximate to the initiator; and ahousing adapted to hold the capacitor discharge unit, the initiator, theinitiating explosive, and the micro-switch together to form anintegrated detonating unit.
 43. The detonator assembly of claim 42,further comprising: an addressable chip; a protection filterelectrically connected to the addressable chip; and a first transformermechanically and mechanically and electrically connected to theaddressable chip and the capacitor discharge unit, wherein theaddressable chip, protection filter, and first transformer are locatedwithin the housing.
 44. The detonator assembly of claim 43, furthercomprising a second transformer electrically connected to themicro-switch, the second transformer adapted to generate a trigger pulseto fire the initiator.
 45. A method for use in a wellbore, comprising:providing a capacitor, an initiator, a micro-switch, an addressablechip, a transformer, and an initiating explosive mechanically andelectrically connected together to form an integrated detonating unit;connecting the integrated detonating unit to an explosive tool;deploying the explosive tool in the wellbore; and firing the initiatorto activate the explosive tool.
 46. The method of claim 45, wherein theexplosive tool is a jet cutter.
 47. The method of claim 45, wherein theexplosive tool is a shaped charge.
 48. The method of claim 47, furthercomprising: selecting the shaped charge to fire from a plurality ofshaped charges deployed in the wellbore.